MKS PI can only be upgraded, in the official version, up to Python 3.7.2 which does not allow klipper to recognize the tapchanger.py file Simply change the code by downgrading.
For more info:
https://github.com/viesturz/tapchanger
https://github.com/viesturz/klipper-toolchanger
The modification is in testing. I am not responsible for any damage that this file may cause.
All credits for Viesturz.